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20_kN

How to extend or reduce your glide ratio if your landing pattern is off?

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I am a student with around 20 jumps. During a coach jump today I messed up the landing a bit. The DZ I jump at is kind of small with limited outs in the area and it's often windy. The wind was a bit unusual today and on my final I ended up landing in a slight downwind condition as opposed to my usual upwind final landing pattern. I miscalculated how much the wind shift would carry me and I ended up in the far corner of the DZ with only a few feet to spare.

I spoke with my coach and she mentioned that one option would have been to execute the final approach in half brakes if I think I am going to come up long. Half brakes would slow my forward speed apparently putting me on the deck sooner. However, this conflicts with other info I have read which says that if you want to extend your glide ratio and travel further with less decent, then fly in half brakes. I asked another instructor and he said that the effect of flying in brakes depends on the wind. If you're far from the DZ and need to maximize your distance over ground and there is a tail wind, fly in brakes. If you have a headwind, flying in half brakes will make things worse.

I am confused and so my questions are:

1. How do I increase my glide ratio if I need to travel further?
2. Without doing risky, low S-turns, how do I decrease my glide ratio if I am coming up long and need to land sooner? Are flair turns the only option?

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Using your rears will increase your glide ratio. Sitting in half breaks with a headwind will reduce the ground distance covered and therefore be beneficial if you are going to over shoot your target, however as it reduces your rate of decent the use of half brakes in a tailwind situation will make you travel further and therefore make your situation worse.

If you are overshooting with a tail wind your options are to increase your ground track to your target, i.e conduct S turns, or increase your rate of descent by using your front risers. Note that this will increase your forward speed as well.

Depending on traffic and obstacles your best bet might be a cross-wind landing.

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the best thing is to have a detail discussion with your instructors to make sure you aren't confused on this topic, everyone learns differently and understands things differently

the words i'd use to explain it are below but i'd also use my hands and pictures:
- flying in brakes decreases your descent rate, you stay in the air longer, that leaves you exposed to the effects of the wind for a longer period of time

- if the wind is at your back (like being upwind and flying back to the DZ) you will travel further because the wind pushes you further, you'll arrive at the dz at a higher altitude, canopy speed plus wind speed = ground speed

- if the wind is in your face your forward speed is reduced so you won't go as far or if the wind is high enough you may go backward, canopy speed minus wind speed = ground speed

- assume canopy speed is 15 mph, wind speed is 11 mph
- flying downwind (with the wind), ground speed would be 26, 15 + 11
- flying upwind (into the wind), ground speed would be 4, 15 - 11
- if the wind speed was 16, flying into the wind, you go backward 1 mph, 15-16
Give one city to the thugs so they can all live together. I vote for Chicago where they have strict gun laws.

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Trying for distance either way, you can reduce your body surface area by pulling your legs up and bringing your arms in close to your body. Less drag means you will get a bit further. It might not be much but sometimes it'll get you to a better landing area.
My computer beat me at chess, It was no match for me at kickboxing....

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Although that works (as CRW-dog, I do it all the time if I need a bit more drive and forward speed relative to the formation), I would rather that a 20-jump student focusses on finding a good out-landing field, rather than try to make the main DZ no matter what.

And the effect of toggles is indeed heavily dependent on the wind. If you are flying with the wind, flying half-brake will extend your glide relative to the ground by letting the wind carry you forward, while the exact same half-brake when flying against the wind will shorten your glide relative to the ground (and could easily push you backwards).

If you use your brakes to let the wind push you back on final, be sure to let them up early enough. A parachute needs a bit of time to recover into full flight, and full flight gives you a good flare.

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IJskonijn

Although that works (as CRW-dog, I do it all the time if I need a bit more drive and forward speed relative to the formation), I would rather that a 20-jump student focusses on finding a good out-landing field, rather than try to make the main DZ no matter what.

And the effect of toggles is indeed heavily dependent on the wind. If you are flying with the wind, flying half-brake will extend your glide relative to the ground by letting the wind carry you forward, while the exact same half-brake when flying against the wind will shorten your glide relative to the ground (and could easily push you backwards).

If you use your brakes to let the wind push you back on final, be sure to let them up early enough. A parachute needs a bit of time to recover into full flight, and full flight gives you a good flare.



Also on some canopies rear risers are much better option if the tailwind is not strong...

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Yup, but its easier to stall a canopy on rears, and that tends to reduce your glide ratio rather drastically.

And for many canopies, half-brakes is not the most optimal for extending glide when flying with the wind. But figuring out the very best way to extend the glide for your specific canopy and wingload is something I don't really expect of a 20-jump student. It is also something that takes a few jumps on that canopy and in different weather conditions to dial in.

So yeah, finding a good landing spot is more important than squeezing every bit of glide out of your wing. Only recently I saw someone make the main landing DZ, flying downwind at ~100ft, and pound the ground when still trying to land against the wind. Had that person picked a field upwind to land in when still at 2000ft, the ambulance could've stayed home...

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It is tricky to provide answers because you really need to know about your own parachute's glide polar -- it's forward and downward speed under every different condition of control application -- and do a little vector math using the canopy's velocity and that of the wind.

Although there are shortcut visual tricks to figuring it out.

So if your parachute is moving forward 30 mph and descending at 8 mph, and there's a 10 mph headwind, the net effect is 20 forward and 8 down. Then you apply brakes or whatever and your canopy in particular with your weight now goes 25 forward and 5 down, the net effect is 15 forward and 5 down.

(And I'm simplifying here by using forward speed of the canopy over the ground, not the actual air speed along the flight path, which is the wind you'll feel in your face.)

In this particular case you went from 8/20= .4 slope to 5/15 = .33 slope downwards. (I'm not bothering to calculate degrees.)

In this case however much brakes you applied, gave a shallower downwards flight path (.33 not .4) and you'll land longer than you would have.

You just need to know your canopy and the result of your control inputs on flight path and speeds and combine that with the unseen wind speed in a trigonomic calculation.

Or........
In practice, you learn to judge these things by seeing what actually happens. You have to know the "accuracy trick" and see what point ahead of you on final approach neither rises nor falls in your line of vision.

So you'll experiment with brake positions on different wind days, no wind, low wind, medium wind, and high. Of course you have to watch out for not stalling, not interfering with traffic, and reattaining sufficient energy and proper flight path before the flare.

A canopy course can help sort some of this stuff out.

There are indeed rules of thumb, where someone might say, "On a typical modern canopy, adding a little to moderate brake with low headwinds on final will result in landing longer. But when the wind gets strong, moderate brake will make you land shorter."

Simple, eh? ;)

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IJskonijn

Although that works (as CRW-dog, I do it all the time if I need a bit more drive and forward speed relative to the formation), I would rather that a 20-jump student focusses on finding a good out-landing field, rather than try to make the main DZ no matter what.
.



Not necessarily the main DZ. Any safe landing area, which, as you correctly say, is the priority. Making oneself smaller should not preclude the ability to select a good landing area.
My computer beat me at chess, It was no match for me at kickboxing....

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